Division of Agriculture and Natural Resources
Division of Agriculture and Natural Resources
Division of Agriculture and Natural Resources
University of California
Division of Agriculture and Natural Resources

News stories

Grow cover crops to attract beneficial insects, add nutrients, suppress weeds and build soil

George Washington, the father of our country, said it well when he proclaimed he grew “crops to eat and sell” and “crops to replenish the soil.”

Generations of farmers follow his footsteps.

Cover crops (also known as green manures) are plants primarily grown for the benefit of the soil rather than for crop yield. With autumn only a few months away, now's a good time to think about planting cool-season cover crop seed mixes for your farm or garden.

Cover crop in a walnut orchard, with flowers to attract beneficial insects, Yolo County, 2018.

Why grow cover crops?

The benefits of cover cropping include reduced soil erosion, adding organic matter, nutrients, and mycorrhizae to the soil, and weed and nematode suppression. Cover crops also increase nutrient retention and water infiltration. And some, such as radish, break into compacted soil layers, making it easier for the following crop's roots to develop more fully. Flowering cover crops on farms also increase beneficial insects, including bees and natural enemies, that provide pollination and pest control services in crop production.

How do cover crops benefit natural enemies?

Beneficial insects need nectar and pollen to survive and reproduce. For example, adult parasitoid wasps feed on flowers, while the parasitoid larvae prey on pests such as aphids, caterpillars, and stink bugs. Lady beetle, aka ladybugs, feed on flowers, especially during times of prey scarcity. In addition to flowers, cover crops, such as vetch and bell (fava) beans, have extra-floral nectaries or spurs at the base of the leaves. These secrete a sugary syrup that attracts beneficial insects, such as syrphid flies to control aphids.

UCCE advisor Rachael Long holding a lacewing, a beneficial insect that feeds on aphids. She is standing in a cover crop in a walnut orchard. (Photo: California Farm Bureau)

Insectary cover crop seed mixes.

Winter mixes that attract beneficial insects (aka Insectary Plants) and fix nitrogen include bell beans, clovers, field peas, and vetch. Other insectary plants to add to a cover crop mix include forbs such as baby blue eyes, poppies, phacelia, purple Chinese houses, sweet alyssum, and tidy tips. Small grains (triticale, barley, and rye) are good pollen sources for beneficial insects. It's a good idea to order insectary cover crop mixes from local sources to avoid potential introduction of non-native forb-type plants from other areas.

Cover crops to perhaps avoid in some crop rotations.

Avoid cover crop species that host arthropod pests or plant pathogens that can damage nearby crops. For example, bell beans are a key host for tomato spotted wilt virus vectored by thrips insects, UC IPM. Mustards attract beneficial insects, but are significant hosts for pests such as stink bugs, cucumber beetles, flea beetles, and lygus bugs. Alfalfa has extra-floral nectaries, but is not a recommended insectary plant because it hosts pathogens, including alfalfa mosaic virus that infects a number of crops, including tomatoes (UC IPM).

How important are floral resources for natural enemies?  

In a 1998 research article, Beneficial insects move from flowering plants to nearby crops, published in California Agriculture journal, I pointed out that beneficial insects extensively use flowering cover crops. In a mark-and-recapture study in an almond orchard with a cover crop, 80 percent of the syrphid flies and 40 percent of the lacewings (both aphid feeders) trapped in the trees fed on flowers and extra-floral resources that the insectary plants provided, as did 10 percent of the parasitoid wasps, which prey on peach twig borer.

Ladybugs primarily feed on aphids, but they will also feed on floral resources during times of prey scarcity.

Balancing multiple needs of cover crops.

Note that legumes need to be mowed or disked prior to full bloom for maximum nitrogen fixation, limiting floral resources. To favor beneficial insects, don't mow or disk all of your cover crop at once; instead, leave occasional strips of flowering plants on your farm. Beneficial insects will find the flowers, as they move around (at least 600 feet for many natural enemies and over a mile for bees). If frost is a concern in your orchard, consider planting strips of low-growing insectary plants, such as tidy tips and other forbs listed above. Be sure to select seed mixes that work with surrounding crops.

George Washington used cover crops to replenish the soil; they're also good for the soul when you savor the benefits, especially all the flowers and beneficial insects attracted to them. Why not play a game of “I Spy” in your cover crop and see if you can find a bumble bee or one of the myriad of natural enemies featured in the UC IPM poster, Meet the Beneficials

 

Multiple benefits of cover crops. (Diagram: Sustainable Agriculture Research and Education Program)

Additional reading

Flowering cover crops support wild bees and a regional sustainability agenda, part of the June 2018 research update in California Agriculture journal.

UC ANR publications on cover crops:

Cover crops for California Agriculture

Cover Cropping for Vegetable Production

Cover Cropping and Conservation Tillage in California Processing Tomatoes

Small Grain Cover Crops

Cowpea Production: Sample Costs and Benefits as a Summer Cover Crop

Cover Cropping in Vineyards: A Grower's Handbook

Cover Crops for Walnut Orchards

Posted on Tuesday, July 17, 2018 at 8:35 AM
Focus Area Tags: Agriculture

Horse country is often in wildfire-prone areas

A population of 700,000 horses call California home and many of them live in areas susceptible to wildfire. UC Cooperative Extension forest and fire advisor Kate Wilkin says says landowners can take advantage of equine grazing habits - eating down to the nub - to create a fire safety zone, reported Denise Steffanus in the Paulick Report.

“Having heavy grazing around your structures and then feathering it out as you go farther away from the structures is one way to protect the property,” Wilkin said. “Of course, you want to be careful not to destroy that forage by overgrazing that will cause erosion.”

Just like all rural residents, horse owners should establish a defensible safety zone around structures, including houses, barns, arenas and other outbuildings. Trees should be thinned to create a 15-foot gap between tree tops and shrubbery cleared so it won't ladder fire from the ground to the canopy.

Wilkin said a larger safety zone can serve as an oasis for horses during a wildfire. 

“For a lot of fires, if you have an irrigated pasture and you can open the gate so the horses can leave if they need to, they will often be OK,” Wilkin said. “Ultimately, you want it to be a large area … it could be an area about half-mile in diameter, and it needs to be that large to keep the heat from affecting your lungs and your horse's lungs. … You can have trees if they are widely spaced and don't have ‘ladder fuel' around them. Then you can have shade on the property but still be more fire safe.”

Wilkin added that farm owners should not rely on a body of water as a firebreak.

“An ember can travel a mile or more during a wildfire,” she said. “While a creek or a larger body of water can slow a fire down, if there are winds and high temperatures, the fire is still going to cross it.”

UCCE forest and fire advisor Kate Wilkin examines a tree with an old fire scar.
Posted on Thursday, July 12, 2018 at 12:55 PM
Tags: Kate Wilkin (6), wildfire (120)
Focus Area Tags: Environment

College students to build apple-picking robots in ASABE competition

For the 2018 ASABE Student Robotics Challenge, teams will simulate the mechanical harvest and storage of apples.

Nineteen teams of college students from top universities in the U.S., Canada and China will compete to build robots to mechanize farm work at the American Society of Agricultural and Biological Engineers Annual International Meeting in Detroit.

The 2018 ASABE Student Robotics Challenge, being organized by Alireza Pourreza, University of California Cooperative Extension agricultural mechanization specialist, will be held on July 31.

“The labor availability for agriculture is decreasing while the need for more food is increasing to feed the growing world population,” said Pourreza, who is based in the UC Davis Department of Biological and Agricultural Engineering. “So agriculture should switch to technologies that are less labor-dependent, such as using more robots, to overcome this challenge.”

Ali Pourreza, shown flying a drone to collect crop data, is organizing the 2018 ASABE Student Robotics Challenge.

The ASABE Student Robotics Challenge provides an opportunity for undergraduate and graduate students to demonstrate their knowledge and skills of robotics in agriculture.

“The goal of this event is to encourage young agricultural engineers to get involved in building robots for agricultural applications and to get experienced as the next generation of farmers,” Pourreza said.

The challenge will be to simulate the harvest and storage of apples, a crop commercially grown in several states. The students will design and operate robots that will autonomously harvest “apples” on field that measures 8 feet by 8 feet. The robots will harvest eight mature apples (red ping-pong balls), remove and dispose of eight diseased or rotten apples (blue ping-pong balls) and leave eight immature apples (green ping-pong balls) on the tree.

This year, the competitors are being divided into a beginner division and an advanced division.

Beginner Teams

California Polytechnic State University        Green and Gold Mustangs
China Agricultural College                          China Ag, Beginners
McGill University                                       We Are Groots
Purdue                                                     ABE Robotics
Purdue                                                     Harvestiers
Texas A&M                                               Texas A&M
University of California Merced                   Bobcats
University of Nebraska Lincoln                    HuskerBots 2
University of Nebraska Lincoln                    HuskerBots3
University of Wisconsin River Falls               Falcon Robotics
Zhejiang University                                    ZJU team 1
Zhejiang University                                    ZJU team 2
Clemson University                                    CARA

Advanced Teams

China Agricultural College                             Dream
McGill University                                          Agrobots
University of Georgia                                    UGA Engineers
University of California – Davis                      Ag-Botics
University of Florida                                      RoboGators
University of Nebraska Lincoln                       HuskerBots 1

The competition will be held in Cobo Center Exhibit Hall, 1 Washington Blvd., Detroit, Michigan. There will be three rounds throughout the day and each team will participate once in each round.

The 2017 robotics challenge was to simulate raspberry cane thinning, removing green canes and pruning the yellow canes.

For more information, visit the 2018 ASABE robotics competition website: https://www.asabe.org/Awards-Competitions/Student-Awards-Competitions-Scholarships/Robotics-Student-Design-Competition.

Video of 2016 competition: https://www.youtube.com/watch?v=U1ymUiCr3Mc

Video of 2017 competition: https://vimeo.com/250379863

 

Posted on Wednesday, July 11, 2018 at 2:12 PM
Focus Area Tags: Agriculture Innovation

More people live in fire-prone communities

As the human population on planet earth, now about 7.6 billion people, continues to grow, more will settle in areas prone to wildfire, reported Mary Beth Griggs in Popular Science magazine.

The reporter spoke with UC Cooperative Extension natural resources advisor Sabrina Drill about wildfire preparation.

First, make sure that an emergency kit is up to date and important papers are in a safe place.

“Know that under conditions of mandatory evacuation, you will encounter traffic, frightening conditions, highly limited visibility due to smoke, etc., so being ready and leaving early is really important,” Drill said.

If there is time, there are important last-minute actions that can be taken to minimize potential fire damage. She suggests moving flammable garden furniture and wood piles away from structures, taking down shade cloths or awnings that could trap embers and making sure doors and windows are closed.

"One thing I would not advise is either leaving sprinklers running or hoping that automatic sprinklers will save a structure, as power may be cut, water lines can melt, and the water and water pressure may be needed by firefighters elsewhere," Drill said.

UC Cooperative Extension provides information to guide actions before, during and after a wildfire on its wildfire resources website.

UCCE natural resources advisor Sabrina Drill is a fire science expert.
Posted on Monday, July 9, 2018 at 3:02 PM
Tags: Sabrina Drill (9)
Focus Area Tags: Natural Resources

Fresno’s Southeast Asian farmers are on trend with new ‘superfood’

Farmer Vang Thao has been managing a successful farm south of Fresno for nearly 30 years, producing a spectacular array of vegetables – heirloom tomatoes, purple bell peppers, water spinach, bitter melon, Thai eggplant and dozens of others.

Every weekend the family traverses the Grape Vine to set up a visual feast at farmers markets in Santa Monica, Hollywood, Palos Verdes, Torrance and Hollywood. Acclaimed Los Angeles chefs rave about his produce, according to a Los Angeles Times feature story on the Thao family.

Produce like sweet potato leaves, amaranth and black nightshade are essential for families hailing from Vietnam, Laos, Thailand, the Philippines and India who seek ingredients for their traditional cuisine, but the market is limited. Now, small-scale farmers like the Thaos are on the cusp of something with much wider appeal.

One of their crops is moringa, a tropical tree that produces an abundance of fresh shoots to sell at the farmers market booth for $1 a bundle. Moringa is a delicate green that can be added to salads, soups and nearly any other dish. It has a pleasant nutty, earthy and slightly pungent green flavor. While it tastes good, it's the plant's nutrient profile that is commanding attention.

Fresno farmer Vang Thao in his moringa plantation.

On the internet, moringas are called miracle trees. All parts of the plant are edible – the tender leaves can be cooked or eaten fresh, moringa flowers are considered a delicacy, the tree's young pods can be used like green beans, roasted seeds are said to have antibiotic and antifungal properties. The roots and bark have medicinal potential, but need more study to determine the right dose. A 100 gram serving of moringa greens has more protein than a cup of milk, more iron than a cup of spinach, and is high in calcium, potassium, vitamin C and vitamin A.

Moringa is the Superfood of 2018, according to the trend watchers at SPINS.com. UC Davis nutrition researcher Carrie Waterman is studying moringa's use, production and processing worldwide. She is pursuing moringa for therapeutic applications in treating cancer, HIV and inflammatory bowel disease.

Vang sells small bundles of moringa shoots at farmers markets for $1 each.

Ruth Dahlquist-Willard, the UC Cooperative Extension advisor to small-scale farmers in Fresno and Tulare counties, recognized moringa's potential to supplement income for Southeast Asian farming families who are marketing specialty Asian vegetables and herbs to immigrant communities.

“Moringa is a drought tolerant tree known for its excellent nutritional content,” Dahlquist-Willard said. “We believe it could improve the economic viability of small-scale farms in our community. We are helping small-scale farmers with moringa product development and marketing.”

Supporting farmers growing moringa in marketing the product to new buyers is an objective of the UCCE moringa project, a partnership with the UC Sustainable Agriculture Research and Education Program, which was funded by a California Department of Food and Agriculture specialty crop block grant. Lorena Ramos, the project lead, is working on developing marketing materials, outreach opportunities, and value-added options.

UCCE moringa project leader Lorena Ramos and Vang Thao with purple bell peppers.

While using moringa is second nature for many immigrant groups, expanding the market includes demonstrating how easily the green can be used in the kitchen. Dahlquist-Willard and Ramos called on another sector of UC Cooperative Extension – the UC CalFresh Nutrition Education Program – for assistance. UCCE offers nutrition education in schools and community settings to children and families eligible for the USDA's nutrition assistance programs. Each year, Fresno State dietetic students serve two-week internships at UCCE. In 2018, one of their tasks was developing creative, healthful recipes incorporating moringa. Among the recipes were overnight oatmeal, pesto, smoothies, guacamole and energy bites – all with moringa.

“We are publishing the best recipes to share with the public to help them add this nutritional green into their diets,” Ramos said.

Recipe cards and moringa samples will be available July 26 at the Fresno Food Expo, where UCCE is hosting a booth to raise awareness about moringa by introducing farmers to Fresno area chefs, buyers and consumers and sharing information about the vegetable's health benefits, culinary versatility and its ability support small-scale farmers in Fresno and Tulare counties.

Fresh moringa can be easily added to many recipes.

Following is a USDA recipe ideal for incorporating moringa:

Grilled quesadilla with vegetables

Ingredients

Nonstick cooking spray
1 medium zucchini, diced
½ broccoli head, diced
1 green pepper, diced
1 medium onion, minced
1 carrot, peeled and grated
16 (6 inch) flour tortillas
12 ounces cheese, shredded
½ cup moringa leaves

Directions

  1. Wash all vegetables.
  2. Collect, dice, shred and measure all ingredients before starting to prepare the recipe.
  3. Spray a large skillet with cooking spray. Add zucchini, broccoli, green pepper, onion and carrot. Cook vegetables on medium heat for 4 to 5 minutes, stirring frequently. Remove vegetables from skillet, and put on a clean plate.
  4. Spray skillet with cooking spray again and place 1 tortilla in the skillet. Top with ½ cup vegetables and 1/3 cup cheese. Sprinkle on fresh moringa leaves.
  5. Place a second tortilla on top. Cook on medium low heat for 2 to 3 minutes or until the cheese starts to melt and the bottom tortilla starts to brown.
  6. Flip over the quesadilla. Cook for another 2 to 3 minutes until tortilla brons.
  7. Repeat steps 4 through 6 to make additional quesadillas
  8. Cut each quesadilla in half or quarters, serve hot with your favorite salsa or other toppings.
  9. Refrigerate leftovers within 2 hours. Eat within 3 to 5 days.

 

UCCE agricultural assistant Michael Yang, left, and Vang Thao snack on a freshly picked melon during a field visit.
 
UCCE nutrition projects coordinator Evelyn Morales demonstrates moringa recipes.
Posted on Monday, July 9, 2018 at 9:03 AM

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